Experiments are proposed that address clinically relevant questions for the management of hearingimpaired patients. The information obtained will assist in deciding which approach for cochlear implantation is most appropriate for a particular patient. Considerable evidence is accumulating that for many patients the preservation of residual acoustic hearing, in addition to the stimulation provided by a cochlear implant, can provide important advantages compared to using only a hearing aid, or only a cochlear implant. One striking advantage is observed for understanding speech in background noise. In addition, this combined acoustic plus electric (A + E) hearing can expand the range of patients that can benefit from electrical stimulation, many of whom were unable to receive adequate benefit from a hearing aid. The proposed studies will continue our ongoing investigation of A + E hearing using the existing Hybrid (short-electrode) device as well as a new generation of longer, less-traumatic electrodes. The advantages and shortcomings of each approach will be measured in terms of preservation of hearing as well as speech understanding in quiet and in noise, for various patients. The goal is to develop eligibility criteria for the different device types, based upon the expected outcomes for various patient characteristics. Additional experiments are described that are designed to discover the mechanisms by which acoustic plus electric stimulation is integrated as an auditory sensation and what factors determine the success of the A + E approach in individual patients.